Solution:
One quick solution is simply Flip the value of "Allow this list to receive e-mail?"

Just go to List Settings

Under Communication, click on "Incoming e-mail settings" link

Select "Allow this list to receive e-mail?" to "No" and click on "Save"

Now, go back to the Incoming e-mail settings again and choose ""Allow this list to receive e-mail?" to "Yes" and then save your changes.

We can also automate the above activities with PowerShell.

Wait, There is an elegant solution yet:
However there is an another efficient way by: Calling RefreshEmailEnabledObjects() method of SPSite object to refresh all Incoming Email settings! (or use: stsadm -o refreshdms command). Here is the PowerShell script: